Angle DCE and Angle EAB are equal because they are alternate angles.
We already know that AB and DC are equal.
Angle DEC and Angle BEA are equal because they are vertically opposite angles.
Therefore, ABE and CDE are congruent because they have two angles that are equal and a side.
so Triangle ABE and CDE are congruent by Angle - Side - Angle (ASA)
